Enter the 6 cruxes which are NOT glowing for you and your teammate.
This will give you the result for the 3 which DO need shooting.
1 through 9 is clockwise.
Complete three times to conclude encounter.
Success will 'Destabilize the obelisk'.
Whoever kills the Tormentor will have the Harmonic Sundering buff for 30 seconds, this person shoots the cruxes.
Dying removes this